The subject matter of this invention relates generally to arc furnace flicker compensators and particularly to load savings over current shutdown devices for arc furnace flicker compensators.
It is known to provide certain kinds of control systems for utilization with arc furnace flicker compensators. In modern VAR generators the controlled power circuit is a thyristor activated inductor which is connected across the power lines, usually on several tens of kilovolts level. Because of the solid state switches, the over current capability of these generators is limited to that of the solid state devices. The problem associated with this kind of circuitry is that the decision whether to stay on line or not under conflicting requirements must be arrived at with the greatest caution and shutdown must not be initiated unless it is absolutely necessary. U.S. Pat. No. 3,686,558 entitled "Control For Frequency Converters" issued to G. Havas et al on Aug. 22, 1972 teaches a logic means for controlling the SCR's of an arc furnace wherein the logic means is responsive to the voltage and current of the main lines and which controls the SCR's in response thereto. However, this patent does not specifically teach the concept of inhibiting or shutting down the circuit after a predetermined number of high current cycles. It would be advantageous therefore for means to be found for shutting down or limiting system currents and voltages under certain operating conditions.